<?php

namespace yyctools\Utils;

class ShortUrlUtils
{
    /**
     * 生成短链接
     * @param $url
     * @param $short_url
     * @param $num
     * @return array
     */
    public static function create($url,$short_url = 'http://www.xxx.com/',$num = 6){
        $charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        $key = 'xxx'; //加盐
        $urlhash = md5($key . $url);
        $len = strlen($urlhash);
        //将加密后的串分成4段，每段4字节，对每段进行计算，一共可以生成四组短连接
        for ($i = 0; $i < 4; $i++) {
            $urlhash_piece = substr($urlhash, $i * $len / 4, $len / 4);
            //将分段的位与0x3fffffff做位与，0x3fffffff表示二进制数的30个1，即30位以后的加密串都归零
            //此处需要用到hexdec()将16进制字符串转为10进制数值型，否则运算会不正常
            $hex = hexdec($urlhash_piece) & 0x3fffffff;
            //域名根据需求填写
            $short = $short_url;
            //生成短网址
            for ($j = 0; $j < $num; $j++) {
                //将得到的值与0x0000003d,3d为61，即charset的坐标最大值
                $short .= $charset[$hex & 0x0000003d];
                //循环完以后将hex右移5位
                $hex = $hex >> ($num - 1);
            }
            $short_url_list[] = $short;
        }
        return $short_url_list;
    }
}